Entamoeba Coli: What is it? Clinical Significance, Morphology, Pathology and Management of Infections Caused by This Parasite

It is a non-pathogenic species of Entamoeba that frequently exists as a commensal parasite in the human gastrointestinal tract.

Differential diagnosis of Entamoeba coli

The differential diagnosis of Entamoeba coli is important in medicine because during microscopic examination of stained stool samples it can be confused with the pathogen Entamoeba histolytica.

This amoeba does not move much with the use of its pseudopod, and creates a movement of place (not progressive) within the large intestine. The amoeba is generally immobile and maintains its round shape.

This amoeba, in its trophozoite stage, is only visible in fresh , unfixed stool samples .

Sometimes Entamoeba coli also has parasites. One is the fungus Sphaerita spp, this fungus lives in the cytoplasm of E. coli.

Although this differentiation is usually done by visual examination of parasitic cysts using light microscopy, new methods have been developed using molecular biology techniques.

The scientific name for amoeba, E. coli, is often confused with the bacterium Escherichia coli. Unlike bacteria, amoeba is mostly harmless and doesn’t cause as many intestinal problems as some strains of Escherichia coli bacteria.

Some of these harmful strains are found within the raw meat that is consumed.

For example, the bacterium Escherichia coli O157: H7, which can cause illness and even death, if ingested.

To make the naming of these organisms less confusing, “alternative contractions” are used to name the species for the purpose of naming ease.

This is why Esch is used. coli and Ent. coli for bacteria and amoeba respectively, rather than using E. coli for both.

Clinical significance

With the presence of Entamoeba coli by itself, doctors do not recommend a treatment, because it is considered harmless.

However, with infestation with this benign entamoeba, other pathogenic organisms can also be introduced, and these other pathogens can cause infection or disease.


All species of entamoeba come in monogenetic forms or have life cycles of one generation.

Entamoeba coli has “three different morphological forms in each life cycle: trophozoite, precystic stage, and cystic stage.”

This life cycle gives rise to the general way in which the Entamoeba species form. This parasite has a large nucleus with a thick membrane that surrounds the nucleus.

There are many chromatins within the nucleus and a large, irregularly shaped karyosome.

Chromatin clumps together, and is unevenly dispersed within the nucleus. The parasite is formed by binary fission like most Entamoeba spp.

The mature cyst is the infectious stage, and it is known to survive longer than those of E. histolytica.

Cysts can survive three to four hours outside the host’s body after desiccation.

Cysts cause infections by consuming contaminated food and drink, such as sewage.

Sometimes insects and rodents are the agents that transmit the parasite to cause infections in food and drink.

Encystment occurs once the cysts are ingested, and they travel to the large intestine.


The trophozoites of E. coli can be distinguished by their broad and conical pseudopods. They are generally confused with E. histolytica due to their overlap in size.

Cysts are distinguished by the presence of eight nuclei found in the mature form.

For the diagnosis of E. coli, a stool sample is usually tested. This is the best method to check if the parasite is E. coli and not E. histolytica.

This usually involves checking the cysts to differentiate them by size, shape, and number of nuclei.

E. coli has cysts in size from 10 to 35 microns, the shape is irregular, oval with a shell-like appearance that is more uniform compared to E. histolytica, and has up to eight nuclei in the cyst compared to the four nuclei of E. histolytica.

When the microbiological testing technician is inexperienced, Entamoeba coli tetranucleated cysts can be mistaken for mature Entamoeba histolytica cysts.

Often times, a tetranucleated Entamoeba coli cyst is larger than a mature Entamoeba histolytica cyst.

Nuclear peripheral chromatin and karyosome are made up of irregular granules’ in this comparison matter.

To make a diagnosis for any species of Entamoeba, usually a wet mount is created, the characteristic cysts are observed by the iodine-stained formalin-ether concentration method, or the trophozoites that are characteristic in a wet preparation or in a preparation are detected. permanent dyed.

In addition, these trichrome stains can be used to mount the cysts of any Entamoeba spp.

Other tests can be used for the diagnosis of Entamoeba spp.

These tests involve the use of laboratory methods and some of these laboratory tests include:

  • The use of optical microscopy (transmission and scanning).
  • Cultivation methods.
  • Isozyme analysis.
  • Antibody detection tests.
  • Antigen detection tests.
  • Immunochromatographic tests.
  • DNA-based diagnostic tests.

Cysts are generally freeze fractured to ensure that samples are easier to examine for comparison of Entamoeba spp.

DNA-based diagnostic tests include the use of DNA extraction, PCR, microarray, and typing methods.

In a DNA-based diagnostic test that is changing the shape of Entamoeba spp. Diagnosis is made faster and more accurately using the ‘Reverse Line Hybridization Assay’ test.

The main objective of this test is to detect and different Entamoeba spp. in stool samples to find the causative agent of amoebic dysentery, E. histolytica.

This test involves the use of gene sequencing and visualization of the different genomes of each Entamoeba spp. Thus helping to detect the deadly E. histolytica.


E. coli are mostly harmless parasites, and they do not harm the host. However, cases of internal bleeding have been reported.

Generally, red blood cells are not found in the cytoplasm of Entamoeba coli, except in rare cases of patients with intestinal bleeding, which causes blood to be observed in the stool of these patients.

These bleeds can lead to intestinal injury.

Other problems caused by E. coli are generally the result of having too many microorganisms in the large intestine, so large populations of E. coli can lead to dyspepsia, hyperacidity, gastritis, and indigestion.

These are the common problems of most parasites that inhabit the intestinal tract.


There is generally no need to administer any treatment to E. coli, due to the rarity of this parasite which becomes infectious.

In an exceptional situation, E. coli was found to be infectious, stool samples and electron microscopy revealed large populations of amoebae within a group of patients with persistent diarrhea.

Some types of treatments may need to be used due to the presence of large populations.

Some arsenical compounds such as carbarone have been shown to treat the trophozoite stage.

Other compounds used to treat large populations of E. coli include diloxanide furoate, and this is generally used in antiamebic therapy.